When in drive the transmission sounds like a lawn mower

Howdy,

My wife drives the van full time, so it is much loved but horribly beat on. I got in today to make a kid run and noticed immediately that it was making a lawn mower like sound from the right front of the van.

I checked the fluid level and it is topped off. When I put the van in neutral and give it some gas there is no lawn mower sound at all.

I have turned my share of wrenches, but I do not have the tools or know how to drop or open up a modern transmission. I would just like some idea of what is going on before I take it to a shop and and they lower the boom on my wallet!

Thanks!

Giff